Fusible element for inclosed electrical fuses.



APPLICATION FILED OCT. 27 I916- Patented May 29, 1917.

INVEN TOR.

A TTORNE Y.

' Hartford, in the county of Hartford and UNITED s ATE-1S ret ial -r? ROBERT C. COLE, OF EARTFOBD, CONNECTICUT, ffasSlGlt'filIt T0 THE JOHN'S-PRATT 60M- IPAINY, OF HARTFORD, CONNECTTCUT, A CORPORATTON 01 CONNECTICUT.

To all whom it may concern: ,Be it known-that T, Rosana C. Conn, a c1t1zen of the United States, residmg at State of Connecticut, have invented a new and useful Improvement in Fusible Elements for Inolosed Electrical Fuses, of which the following is a specification.

- This invention relates to the construction of overload has been reached. To accompl h this links in the form of flat strips.

h e been calibrated by cutting away. portions of the edges or perforating the strips at the middle, and numerous expedients have been sug ested to likewise calibrate round wire fusi l e links. It is well known, however, that fusible links of circular cross section are inclined to hang, that is, are

Y sluggish and tend to remain in a molten condition when a graduallyinoreasing overload reaches its maximum so that the fuse does not open and protect the circuit when it is desired it should. I

The object of the present invention is to in a very simple way accomplish. the calibration of multiple strip fusible elements in which the links are made ofround wire or are circular in cross section. This objectis attained by bending. the fusible links so that they approach and touch or almost touch each other at the middle of the fuse, thereby increasing theheating efiect at the middle y reducing the heat conducting capacity of the filling by which they are surrounded at that point. This concentration of heat in this manner at the middle reduces the overload carrying time without affecting the normal carrying capacity, and causes the links to melt or blow at the center at the FUSIBLE ELEMENT 30E ENCLOSED ELEGTBTGAL FUSES.

Specification of Letters Patent. Patented May 29, 191?.

Application filed @ctoher 27, 1916.

Serial No. 127,990.

by the dotted line 33 on Fig. 1. Fig. 4.

The insulating tubular casing 1 with the metallic end caps 2 and exterior knife-blade terminals 3 are of common form and construction and, of course, these may be varied in size, shape and style.

The fusible element has terminals which extend through the end caps and are fastened to the knife-blade exterior terminals. 011 the inner ends of the fusible element terminals are frames or disks 5 of conducting' material, and secured to these disks or frames are the ends of the fusible links 6. These links, of which there may be any desired number depending upon the rated carrying capacity of the fuse, are of compact cross section, desirably circular, and although spaced apart at each end, they are brought together so as to touch or almost touch at the middle of the casing. The links may be brought together by bending them inward sharply, as shown in Fig. 1, or they may be brought together gradually, as shown in Fig. 4. The fusible element thus formed is placed in the casing which is then filled with granular heat insulating and electrical non-conducting material of approved condensing composition 7 As a result of this construction each link tends to heat the others at the middle when a maximum current is flowing, owing to the proximity of the links at the middle, to the reduction of the effective filling material between the links at the-middle, and to the increased-amount of filling material outside of the links at the middle so that there is less radiation at the middle than at the ends to the tube and outer atmosphere. These facthe element will melt more quickly at the middle of its length than with the ordinary straight round wire links which are sluggish and uncertain. This construction makes it [possible to calibrate a fuse so as to obtain a short predetermined blowing time on hot or coldoverload. The invention claimed is; I

l. fusible element for an inclosed fuse consiming of a plural number of fusible raj links of compact cross section spaced apart at their ends and broughtinto proximity with each other at the middle of their length. I

,2. A fusible element for an inclosed fuse consisting of a plural number of fusible links of round cross section spaced apart at their ends and brought together intermediate the ends.

3. A fusible element for an inclosed fuse consisting of a plural number of. fusible links of compact cross section held in proximity With each other at the vmiddle and spaced apart at the ends, conducting. frames holding the ends of the links apart, and terminals extending from the conducting frames.

4. A fusible element for an inclosed fuse consisting of a plural number of round fusible Wires, saidwires being closer together at the middle than at their ends, disks holding the ends of the Wires apart, and terminals extending from the disks.

5. A fusible element for an inclosed fuse consisting of a plural number of round fusible Wires brought together at the mid dle and held spaced apart at the ends.

ROBERT C. COLE Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents,

Washington, D. G. 

